Braking systems
Braking systems covers hydraulic principles, component function, bleeding and fault diagnosis, including ABS awareness.
Hydraulic principle
Pascal's law states that pressure applied to a confined fluid is transmitted equally in all directions. A small master-cylinder piston creates pressure that acts on larger wheel-cylinder or caliper pistons, multiplying force. The vacuum servo reduces pedal effort; disc brakes self-adjust, while drum brakes use a self-adjuster and return springs.
Worked example. A master-cylinder piston has an area of 5 cm² and is pushed with 500 N. Pressure = force ÷ area = 500 ÷ 5 = 100 N/cm². A caliper piston of 20 cm² receives 100 × 20 = 2,000 N. Because the larger piston moves less distance, pedal travel is longer - force is multiplied, not work.
Bleeding and diagnosis
Bleed from the wheel furthest from the master cylinder to the nearest, keeping the reservoir above minimum. Never let the reservoir run dry. Brake fluid is hygroscopic; DOT 4 must not be mixed with DOT 5 silicone fluid. Spongy pedal means air in the system; a pedal that sinks under steady pressure means an internal leak or failing master cylinder.
Traps
Bleeding in the wrong order. Pushing contaminated fluid back through an ABS modulator. Letting a caliper hang by its hose. Fitting pads without cleaning and greasing the sliders. Ignoring brake fade caused by overheating.